Using crowdsourcing for deep learning
First thing, you need to give more credit to more reliable users. You can establish the credit from amount of data they send, and a feature, where other users can review other's feed and classify it. From there, you will have a measure of certainty to what data is good and what is not.

You will need to implement a centralized server, unless you're trying to do some kind of a peer-to-peer trust systems, but I don't think smartphones are powerful enough to do training themselves.

You will need big machines for training NNets. Don't trust users to have them. You would end up with tons of badly trained NNets, which don't make for a good CoM.